“The only eyewitnesses to come forward saw a single speeding car,” said Capt. Mike Parker.

Parker said the department had heard rumors about a street race in the area but had not been able to verify it.

Walker, 40, and his friend, whom witness Jim Torp identified as Roger Rodas, took a red Porsche out for a spin as a charity event held in support of Walker’s organization Reach Out Worldwide was winding down.

Torp said he heard a loud boom and knew his friends had been in an accident. The smoke from the crash was visible from Always Evolving Performance Motors, which Rodas owned and where car enthusiasts and supporters were still gathered -- some thinking it was just a fire on a nearby hill.

Jim Torp's son, Brandon, 28, grabbed a fire extinguisher and headed up the hill, followed by about 20 other workers, the elder Torp said.

Speed may have been a factor in the crash, which occurred about 3:30 p.m. on Hercules Street, a normally quiet road with a 45-mph speed limit, authorities said. Walker was apparently the passenger in the 2005 red Porsche Carrera GT.

The four-lane road up the hilly street has signs warning drivers to slow down as they approach an uphill curve near the site of the accident.

The fiery crash left charred trees in the secluded area near a business park, and a burned smell lingered in the air Sunday. The car, which was reduced to an ashen hulk, had toppled a tree and a concrete lamp post, which crews from Southern California Edison removed Sunday. Looping tire tracks were visible on the asphalt nearby.

Investigators are looking at whether the tire tracks are related to the crash, but the investigation is ongoing, said sheriff’s Deputy Peter Gomez. There probably will not be an update on the investigation until Monday, he said.

Because of the condition of the bodies, which were badly burned, dental records will be used to positively identify the victims, said Los Angeles County coroner's investigator Dana Bee. Autopsies have not been scheduled.

Torp said his son saw his two friends burn in the car before the fire department arrived. Officials at the scene held back a childhood friend of Walker from pulling his body from the burning car, and firefighters had to pull Rodas’ young son away from the wreckage, Jim Torp said.

Eduardo Luna, who owns the warehouse across from where the event was held, saw the Porsche leave the parking lot moments before the crash. Ten minutes later, he heard about the accident and ran down to Hercules Street, where he saw the car in flames.

"They just didn't want to believe this happened," Torp told fans and media at the crash site on Sunday. "It was 'Fast and the Furious,' that's what it is. Both race car enthusiasts, both loved speed, both knew how to handle cars, and this had to happen."

Walker was in good spirits earlier in the afternoon and overwhelmed by the event’s success, Torp said. The parking lot of the shop had been full of high-performance cars, and he and Rodas were greeting people, shaking hands and enjoying themselves.

Reach Out Worldwide was formed in 2010 as a quick-response first-aid organization, and the event was one of many car shows Rodas helped put on each month, Torp said. Proceeds were to be donated to families affected by the typhoon in the Philippines and a tornado in Indiana, Torp said.

When Rodas' wife and young daughter arrived at the Always Evolving warehouse after the accident, Torp said he heard screaming through the doors after they learned of Rodas' death.

Rodas, 38, was active in philanthropy and supported several charities through his racing. He competed in 10 Pirelli World Challenge GTS races in 2013, according to the racing organization. Torp, who with his son has worked with Always Evolving for several years, described Rodas as a compassionate, fun man who cared deeply about others and "loved his American cars as much as he loved his $500,000 cars."